Annihilation diagram contribution to charmonium masses |
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| Authors: | Renqiang Zhang Wei Sun Feiyu Chen Ying Chen Ming Gong Xiangyu Jiang Zhaofeng Liu |
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| Affiliation: | 1. Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China2. School of Physics, University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | In this work, we generate gauge configurations with \begin{document}$ N_f = 2 $\end{document}![]() ![]() dynamical charm quarks on anisotropic lattices. The mass shift of \begin{document}$ 1S $\end{document}![]() ![]() and \begin{document}$ 1P $\end{document}![]() ![]() charmonia due to the charm quark annihilation effect can be investigated directly in a manner of unitary theory. The distillation method is adopted to treat the charm quark annihilation diagrams at a very precise level. For \begin{document}$ 1S $\end{document}![]() ![]() charmonia, the charm quark annihilation effect barely changes the \begin{document}$ J/\psi $\end{document}![]() ![]() mass, but lifts the \begin{document}$ \eta_c $\end{document}![]() ![]() mass by approximately 3–4 MeV. For \begin{document}$ 1P $\end{document}![]() ![]() charmonia, this effect results in positive mass shifts of approximately 1 MeV for \begin{document}$ \chi_{c1} $\end{document}![]() ![]() and \begin{document}$ h_c $\end{document}![]() ![]() , but decreases the \begin{document}$ \chi_{c2} $\end{document}![]() ![]() mass by approximately 3 MeV. We did not obtain a reliable result for the mass shift of \begin{document}$ \chi_{c0} $\end{document}![]() ![]() . In addition, we observed that the spin averaged mass of the spin-triplet \begin{document}$ 1P $\end{document}![]() ![]() charmonia is in good agreement with \begin{document}$ h_c $\end{document}![]() ![]() , as expected by the non-relativistic quark model and measured by experiments. |
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| Keywords: | lattice disconnect distillation hyperfine splitting |
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